Energy recovery apparatus

ABSTRACT

An energy recovery pump-motor including an energy recovery pump and a mixed-phase motor for replacing conventional valves in fluid circuits such as an absorption refrigeration system. The energy recovery pump pressurizes a first liquid by recovering flow work energy from a second liquid. The mixed-phase motor recovers flow work energy and expansion energy from a high pressure, saturated third liquid and transfers the energy along a shaft to the pump to aid in pressurizing the first liquid. The energy recovery pump is shown in a single effect absorption refrigeration system, while the pump-motor is shown in both single effect and double effect systems.

The application is a division of U.S. patent application Ser. No.062,232, filed June 15, 1987, now U.S. Pat. No. 4,793,153.

FIELD OF THE INVENTION

The present invention is directed to devices capable of recoveringenergy otherwise lost in refrigeration or heating fluid circuits. Thepresent invention relates to integrating a device comprising an energyrecovery pump and a mixed-phase motor for use in a fluid circuit,typically an absorption refrigeration system.

BACKGROUND OF THE INVENTION

The present invention is particularly applicable to an absorptionrefrigeration fluid system. The essentials of such a system are shown inFIG. 1 (although heat exchangers are omitted for the sake of clarity).In a typical system like that of FIG. 1, a refrigerant, e.g., water orother phase change substance, is dissolved in an absorbent, e.g.,lithium bromide or some other salt. The two materials are often called a"solution pair". The refrigerant is absorbed or desorbed in or out ofsolution with the absorbent to varying degrees throughout the system,and the heat of absorption is added or extracted to produce heating orcooling effects. Another common solution pair used in an absorptionrefrigeration system is ammonia as the refrigerant and water as theabsorbent.

With reference to FIG. 1, the solution enters the desorber 12 (sometimescalled a generator). Heat, Q1, is added to desorber 12. Refrigerantboils off as a vapor leaving what is termed a weak solution. The weaksolution returns to absorber 14 via lines 16 and 18 through valve 20.The vapor refrigerant flows via line 22 to condenser 24. Externalambient cooling condenses the refrigerant vapor to a liquid, giving offheat, Q2. The liquid refrigerant flows via lines 26 and 28 through valve30 to evaporator 32. In a refrigeration system, the heat, Q3, gained inthe evaporator is from the cooling load. The vaporized refrigerant flowsfrom evaporator 32 via line 34 to absorber 14. The vapor refrigerant ismixed with weak solution in absorber 14, giving off heat, Q4, to createstrong solution which is then pumped at pump 36 through lines 38 and 40from absorber 14 to desorber 12 so that the cycle may continue. Althoughnot shown, system 10 ordinarily includes a first heat exchanger of sometype to include lines 40 and 16 and a second heat exchanger to includelines 26 and 34.

The strong solution in an absorption refrigeration system is a liquidand, consequently, is more easily pumped and pressurized than a vapor.Nevertheless, mechanical energy is added to the system at pump 36. Afterthe refrigerant is vaporized with externally added heat and separatefrom the strong solution, the refrigerant is liquified and reduced inpressure so that, as indicated, at the evaporator, heat may be readilyand beneficially absorbed. Thus, valve 30 functions to controllablyreduce the pressure of the liquid refrigerant from condenser 24.Typically, the refrigerant is saturated or nearly saturated at that timeso that when it passes through valve 30, some of it changes phase and isvaporized. To the degree pressure is reduced and a phase change takesplace, energy is lost. Additionally, the weak solution from desorber 12is depressurized to mix with the depressurized refrigerant in absorber14. Consequently, energy is again lost at valve 20. Thus, although anabsorption refrigeration system is widely used, the conventional systemrequires a significant amount of energy and, once used, rejects itwithout reusing or recovering it. The strong solution is pressurized sothat the heat rejection portion of the thermodynamic cycle of therefrigerant may take place at a temperature and pressure level whichallows the subsequent heat absorption portion of the cycle to take placeat a useful level relative to the heat sink, i.e., the environment to bebeneficially cooled.

U.S. Pat. No. 1,866,825 shows an expansion engine in the form of helicalgears for expanding vapor leaving a desorber and also expanding weaksolution leaving the desorber to reduce the heat and high pressure ofeach fluid and recover the energy thereby to help drive a pump for thestrong solution. Smith understood the loss of energy in usual absorptionrefrigeration systems and presented a device intended to recover some ofthat energy. The device of Smith, however, was apparently neversuccessful. In any case, a helical gear-type engine is complex andundoubtedly excessively expensive in a modern economy.

U.S. Pat. No. 4,646,541 indicates that various types of motors could beused to reduce pressure in the weak solution and liquid refrigerantstreams of an absorption refrigeration system to recover some energy andreduce the requirement of external power for the pump. An expansion,rotary-turbine type engine is disclosed. Although not as complicated asa helical gear engine, a turbine type engine does not provide positivefluid control and presents sealing and other engineering challenges.

Thus, the art does not teach piston devices for recovering the energy inan absorption refrigeration system. In this regard, however, althoughnot a piston device, U.S. Pat. No. 3,791,768 shows a dual chamberdiaphragm fluid pump wherein energy from one stream could be used topump energy in another stream.

As a consequence, the present invention is directed to recovering energywith piston devices from locations in fluid circuits where valves arenow commonly used to provide a controlled depressurization.

SUMMARY OF THE INVENTION

The present invention is directed to energy recovery apparatus and anabsorption refrigeration and/or heating system in which such apparatusis incorporated. The energy recovery apparatus includes a piston pumpand a piston motor, wherein there is mechanism for connecting thepistons of each for simultaneous movement, as well as mechanism forswitching from one pump stroke to another and from one motor stroke toanother at the same time. The pump includes a first cylinder with afirst piston therein to divide the first cylinder into a driving chamberand a pumping chamber. The pump has mechanism for filling the pumpingchamber with a first liquid of first pressure. The pump further hasmechanism for driving the first piston in a pumping stroke with a secondliquid at a second pressure. The pump also includes mechanism forreleasing the first liquid from the pumping chamber during the pumpingstroke. The pump further includes mechanism for returning the firstpiston in a filling/exhausting stroke. The pump also has mechanism forexhausting the second liquid from the driving chamber during thefilling/exhausting stroke with a second cylinder. The motor of theenergy recovery apparatus includes a block and a driven member in theform of a second piston operably mounted with respect to the block. Themotor also has mechanism for driving the driven member. The drivingmechanism includes mechanism for metering a discrete quantity of secondliquid to drive the driven member at a third pressure through ahydraulic power stroke. The driving mechanism further includes mechanismfor expanding the quantity of metered second liquid wherein at least aportion of the second liquid changes phase to drive the driven member ina return direction at a pressure lower than the third pressure throughan expansion power stroke.

Although in the most general embodiment as indicated, the pump has apiston and the motor has a piston, in a preferred embodiment, each ofthe pump and motor have aligned dual chambers with a piston in each andwith the pistons connected to one another. Furthermore, as indicated,the set of pistons from the pump are connected with the set of pistonsfrom the motor so that they operate in tandem. In this way, the pump notonly advantageously recovers energy from a high pressure stream ofincompressible liquid and uses it to pump a lower pressure stream, butthe motor aids in this process by recovering energy from a highpressure, saturated or near saturated incompressible liquid stream whichgives up mechanical energy during a controlled hydraulic flow andexpansion energy during a phase change.

An absorption refrigeration and/or heating system may advantageouslyinclude energy recovery devices. In a general system, an absorptionrefrigeration and/or heating fluid circuit includes a desorber, acondenser, an evaporator, an absorber, and mechanism for fluidlycommunicating between these various devices. The desorber absorbs heatand at a relatively high pressure vaporizes a first volume ofrefrigerant from a second volume of strong solution to result in a thirdvolume of weak solution. The condenser releases heat and condenses thevapor refrigerant to liquid refrigerant at the high pressure. Theevaporator absorbs heat and evaporates the liquid refrigerant at the lowrelative pressure. The absorber releases heat and absorbs the evaporatedrefrigerant into the weak solution at the low pressure to form newstrong solution. The fluid communicating mechanism includes devices forincreasing and decreasing pressure as appropriate. In accordance withthe present invention, the communicating mechanism includes mechanismfor recovering energy from the high pressure weak solution in order topump the low pressure, strong solution. The energy recovery mechanismincludes first and second aligned cylinders with first and secondpistons therein, respectively, and a rod connecting the pistonstogether. The energy recovery mechanism is structured so that the squareof the ratio of the rod diameter to the cylinder diameter is equal tothe ratio of the volume of the refrigerant vaporized in the desorber tothe volume of strong solution entering the desorber. The presentinvention in this general form is particularly advantageous in thatdefinite flow control is maintained with respect to the various fluids,i.e., the strong and weak solutions and the refrigerant, as indicated.Such control is possible through the use of a piston device structuredas described in detail hereafter.

In a preferred embodiment, the energy recovery mechanism used in theabsorption refrigeration and/or heating system also includes a motor asdescribed hereinbefore. In this way, the energy recovery pumpadvantageously recovers hydraulic or flow work energy from the liquidweak solution, while the motor recovers both hydraulic energy and phasechange expansion energy from the liquid refrigerant as it passes fromthe condenser and partially vaporizes on its way to the evaporator. Theenergy recovered is used to pump strong solution from the absorber tothe desorber.

Although the invention has been thusly summarized, preferred and otherembodiments and the advantages of the invention are further describedand explained and may be better understood by reference to the followingdrawings and the detailed descriptive matter thereafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a prior art absorptionrefrigeration system;

FIG. 2 is a schematic illustration of an absorption refrigeration systemincorporating the energy recovery pump-motor in accordance with thepresent invention;

FIG. 3 is a schematic illustration similar to FIG. 2 incorporating anenergy recovery pump in accordance with the present invention;

FIGS. 4A and 4B are schematic illustrations of the energy recoverypump-motor showing configurations for oppositely directed strokes of thepistons in accordance with the present invention;

FIG. 5 is a schematic illustration of a prior art double effectabsorption refrigeration system;

FIG. 6 is a schematic illustration of the system of FIG. 5 whereinenergy recovery pump-motors in accordance with the present inventionhave replaced the valves and pump of the prior art system; and

FIG. 7 illustrates a typical pressure versus specific volume phasediagram for an absorption refrigeration system.

DETAILED DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

Referring now to the drawings wherein like reference numerals designateidentical or corresponding parts throughout the several views and, moreparticularly, to FIGS. 4A and 4B, an energy recovery pump-motor inaccordance with the present invention is designated generally by thenumeral 50. FIG. 4A shows pump-motor 50 in a first configuration whereina first piston from pump 52 is in a pumping stroke and a first pistonfrom motor 54 is in an expansion power stroke, while FIG. 4B showsrecovery pump-motor 50 in a second configuration wherein a second pistonof pump 52 is in a pumping stroke and a second piston from motor 54 isin an expansion power stroke, while in the second configuration thefirst piston in the case of pump 52 is returning and serving a filling,charging, or exhausting function and the first piston in the case ofmotor 54 is in a hydraulic power stroke. Considering FIG. 4A, energyrecovery pump 52 includes a casing 56 which forms first and secondcylinders 58 and 60 on opposite sides of a common wall 62. Casing 56includes with respect to cylinder 58 a wall 64, opposite common wall 62with a wall 66 therebetween to form the cylindrical cavity. Similarly,casing 56 includes with respect to second cylinder 60 a wall 68 oppositecommon wall 62 with a wall 70 therebetween to form another cylindricalcavity.

Pump 52 includes first and second pistons 72 and 74 which divide firstand second cylinders 58 and 60 into first and second driving and pumpingchambers 76, 78, 80 and 82, respectively. A rod 84 extends throughcommon wall 62 and attaches at opposite ends to pistons 72 and 74. Rod84 passes through driving chambers 76 and 80. As in other similarapplications throughout this disclosure, it is understood that seals,bearings, and other such mechanisms are used with respect to thepistons, rods, shafts, etc. in a fashion known to those skilled in theart.

Pump 52 is structured so that a low pressure, first liquid is pumped toa higher pressure by a high pressure, second liquid which then exhaustsat a lower pressure. The low pressure, first liquid alternately entersone of pumping chambers 78 and 82 of casing 56 via lines 86 and 88through check valves 90 and 92, respectively. The first liquidalternately exhausts from one of pumping chambers 78 and 82 via lines 94and 96 through check valves 98 and 100, respectively. As shown in FIG.4A, in a first half cycle with four-way, two-position valve 106 in itsfirst position, the high pressure, second liquid enters driving chamber76 via lines 102 and 104 through valve 106. At the same time, secondliquid at a lower pressure exhausts from driving chamber 80 via lines108 and 110 through valve 106. As shown in FIG. 4B, in a second halfcycle, with valve 106 in its second position, the high pressure, secondliquid enters driving chamber 80 via lines 102 and 108 through valve106. At the same time, second liquid at a lower pressure exhausts fromdriving chamber 80 via lines 104 and 110 through valve 106.

For similar reasons, check valve 92 opens so that pumping chamber 82fills with low pressure, first liquid at the same time, low pressuresecond liquid exhausts from driving chamber 80. When valve 106 changesposition from the first position shown in FIG. 4A to the second positionshown in FIG. 4B, first liquid flows into driving chamber 80 and flowsfrom driving chamber 76 so that pistons 72 and 74 change direction oftravel. In FIG. 4B, high pressure, second liquid flows into drivingchamber 80 and hydraulically expends energy to drive piston 74, therebypumping high pressure, first liquid from pumping chamber 82. In thiscase, the pressurizing of first liquid in pumping chamber 82 keeps checkvalve 92 closed and allows check valve 100 to open. Check valve 90 opensso that pumping chamber 78 fills with low pressure, first liquid. At thesame time, low pressure, second liquid exhausts from driving chamber 76.

Operationally in FIG. 4A, high pressure, second liquid flows intodriving chamber 76 and hydraulically expends energy to drive piston 72,thereby pumping high pressure, first liquid from pumping chamber 78. Thepressurizing of first liquid in pumping chamber 78 keeps check valve 90closed and allows check valve 98 to open.

Pistons 72 and 74 preferably travel to near the end walls of first andsecond cylinders 58 and 60. A limit switch 112 senses piston 72 as itapproaches end wall 64. Limit switch 112 communicates electrically vialine 114 with solenoid 116 of valve 106 which causes valve 106 to switchfrom its first position to its second position. Switch 112 and solenoid116 are in electrical communication with an electrical source via lines118 and 120.

Likewise, when piston 74 is in a pumping stroke and approaches end wall68, limit switch 122 senses piston 74 and communicates via line 124 withsolenoid 126 of valve 106. Switch 122 and solenoid 126 are in electricalcommunication with an electrical source via lines 128 and 130.

Motor 54 includes a block 132 which is similar to casing 56. Block 132forms first and second main chambers 134 and 136, preferablycylindrical, with a common wall 138 therebetween. Block 132 includes anend wall 140 opposite common wall 138 with a wall 142 extendingtherebetween to form the cavity of first cylinder 134. Block 132 alsoincludes an end wall 144 opposite site common wall 138 with wall 146extending therebetween to form the cavity of main chamber 136.

First and second pistons 148 and 150 divide first and second mainchambers 134 and 136 into first and second portions or charging andexhaust chambers 152, 154, 156, and 158, respectively. A rod 160 alsoextends through common wall 138 and attaches at opposite ends to firstand second pistons 148 and 150. Rod 160 also extends through firstportions 152 and 156. A drive shaft 162 provides a solid connectionbetween piston 72 of pump 52 and piston 150 of motor 54. Drive shaft 162extends through second portion 158 and end wall 144 of motor 54, as wellas through end wall 64 and pumping chamber 78 of pump 52. Drive shaft162 transfers energy recovered by motor 54 to pump 52 thereby allowingpump 52 to pressurize the first liquid to a greater level than wouldotherwise be possible.

Motor 54 also includes an eight-way, two position valve 164. Valve 164has a first position, as shown in FIG. 4A, placing charging chamber 152in fluid communication with the high pressure, saturated third liquidvia lines 166 and 168 through valve 164 and placing exhaust chamber 154in fluid communication with drain line 170 via line 172 and valve 164.At the same time, what was first portion 156 and second portion 158 areplaced in fluid communication with one another through valve 164 vialines 174 and 176 to form a single motor chamber. In this way, the highpressure saturated third liquid in the first portion 156, part of theunified motor chamber expands into the exhaust chamber 158 part. Indoing so, at least a portion of the liquid changes phase to become avapor and forces piston 150 toward common wall 138. At the same time,hydraulic or flow work energy is expended on piston 148 as first portion152 of the other chamber 136 is filled. Expended liquid/vapor exhaustsfrom second portion 154 of chamber 136.

To insure that valve 106 of pump 52 and valve 164 of motor 54 changeposition at the same time, a rod 178 is illustrated as connecting thetwo valves together. It is understood that rod 178 is illustrative ofthe necessity to shift the valves at the same time and that theparticular mechanism could be electrical or of some other appropriatetype. In any case, since valves 106 and 164 shift at the same time, theswitches 112 and 122 operating solenoids 116 and 126 also function tosense the ends of travel of the pistons so that separate sensing devicesare not needed for motor 54. In this regard, it is understood that thesensing devices could be associate with motor 54 instead of pump 52 orthat one device on one of pump 52 and motor 54 could sense the end oftravel in one direction of the various pistons, while another device onthe other of pump 52 and motor 54 could sense the end of travel of thepistons in the other direction. It is further understood that theswitches 112 and 122 could take a variety of forms. They could sense,for example, motion based on mechanical, electrical, magnetic,hydraulic, or other physical principles. In like fashion, they couldcommunicate with the relevant valve via a signal that is mechanical,electrical, magnetic, hydraulic, or a signal of some other physicaltype. The important consideration is that the end motion of the pistonsis sensed in both directions and that an appropriate signal is sent tothe control mechanism for switching the valves.

It is preferable to maintain symmetry between the sides of pump 52. Inthis way, each side will function 180° out of phase with the other, andthere is no need for synchronizing mechanism or concern of mechanicallockup. Thus, it is understood that the cylinders and pistons havesimilar diameters and lengths and that rod 160 has a constant diameter.Since pump 52 functions with liquids which are essentiallyincompressible, the reduction of chamber 78 by the presence of driveshaft 162 must be compensated for in chamber 82. Therefore, to maintainthe symmetry of pumping chambers 78 and 82, a dummy shaft 180 extendsfrom piston 74 to wall 68 at all points along the travel of piston 74.Dummy shaft 180 may telescope into piston 74 and connecting rod 84 asillustrated by the broken lines, or dummy shaft 180 may extend throughwall 68 (not shown) and reciprocate as appropriate. It is noted that ifdummy shaft 180 were to extend through wall 68, it could transfer energyto another use device.

Likewise, it is preferable for symmetry to be maintained with respect tochambers 154 and 158 of motor 54. In this regard, a dummy shaft 182 mustextend from piston 148 to wall 140 at all points along the travel ofpiston 148. As with dummy shaft 180, dummy shaft 182 may telescope intopiston 148 and main shaft 160, as indicated by the broken lines, or itcould also extend through wall 140 and reciprocate as appropriate. Withrespect to dummy shaft 182, however, its presence is not necessarilyrequired. Since a high pressure, saturated third liquid at leastpartially vaporizes during the expansion power stroke of one or theother of the pistons, the vapor could compress or expand as necessary tocompensate for any asymmetry.

FIG. 4B is the same as FIG. 4A, except valve 164, along with valve 106,is shown in a second position. Consequently, a high pressure, saturated,third liquid is filling charging chamber 156. Spent liquid/vapor isexiting chamber 158. Chamber 152 and chamber 154 are in fluidcommunication with one another to form a single motor chamber for thepower stroke of piston 148.

It is observed that motor 54 is more fully described in a U.S. patentapplication Ser. No. 062,232, filed June 15, 1987, hereby incorporatedby reference.

Operation

The energy recovery pump 52 and the mixed phase motor 54 of the energyrecovery pump-motor 50 operate in unison with respect to one another.Since each uses different fluids of the fluid system in which a recoverypump-motor is incorporated, for the sake of clarity the operation ofeach is separately described. Because of the requirement that the valvesshift at the same time and the pistons be mechanically connectedtogether, it is clear, however, that the two devices cooperate totransfer energy from the second and third liquids to the first liquid.

With reference to FIG. 4A, low pressure first liquid enters the front ofcylinder 60, otherwise called pumping chamber 82. The first liquidenters through intake check valve 92. First liquid does not flow throughcheck valve 90 into the front of cylinder 58 because the pressure onthat side of the pump is at the higher pumping pressure. At the sametime, high pressure second liquid flows through two-way valve 106 andenters the back of cylinder 58, otherwise called driving chamber 76. Thecombination of the pressures of these two incoming liquids move thepistons to the right, as shown by the arrow. As a consequence, fluid infront of piston 72, that is, fluid in pumping chamber 78, is forced outthrough check valve 98 at the higher pump pressure. The piston motionalso forces the now-depressurized second liquid from the back of piston74, that is, from driving chamber 80, through valve 106 to a lowerpressure drain line. When the end of the stroke is reached, sensingdevice 112 senses piston 72 and sends a signal to solenoid 116 to shiftvalve 106 thereby reversing the flow of the second liquid with respectto cylinders 58 and 60 and which shortly thereafter causes the flow offirst liquid with respect to cylinders 58 and 60 to reverse. The valveswitching and reversal of flow with respect to cylinders 58 and 60, inturn, reverses the direction of travel of pistons 72 and 74, so thatpump 52 operates in the same fashion in the reverse direction and thencontinues to cycle.

Mixed phase motor 54 captures flow-work or hydraulic energy from thehigh pressure third liquid, and also captures expansion energy when thesaturated or near saturated third liquid drops in temperature andpressure to form a mixture of vapor and liquid. Useful energy extractionin these two forms appears as linear shaft work at drive shaft 162.

Motor 54 is shown in FIGS. 4A and 4B with dual main chambers orcylinders and connected pistons. In FIG. 4A, first portion 152 of mainchamber 134 is filling with high pressure third liquid through valve164. Hydraulic flow-work is done on piston 148 as the fluid expandsfirst portion 152. At the same time, first portion 152 of chamber 134functions to meter a specific quantity of the incompressible thirdliquid into that half of motor 54. Second portion of chamber 154, on theother side of piston 148, contains a lower temperature and pressureliquid/gas mixture which is exhausting through valve 164. What werefirst and second portions 156 and 158 of main chamber 136 of motor 54are in fluid communication with one another through valve 164 to form asingle motor chamber. The hot pressurized liquid/vapor mixture incombined chambers 156 and 158 seeks an equilibrium pressure based onavailable volume. The pressure acts on the entire area of the face ofpiston 150 less the small area represented by the cross-section of driveshaft 162. Such force is only opposed by the force applied by thepressure to the very small area of piston 150 facing into first portion156. Since main shaft 160 has a relatively large diameter, the face areaof piston 150 on the chamber 158 side is significantly greater than thearea of the face of piston 150 on the chamber 156 side. Therefore, whenchambers 156 and 158 are placed in fluid communication with one another,fluid pressure equalizes and when acting on the larger area causes aforce to expand chamber 158 and move piston 150. The expansion energy onpiston 150, along with the flow-work energy on piston 148, transmitsforce along drive shaft 162.

When pistons 148 and 150 reach the full extent of intended travel, valve164 switches in response to the connection with valve 106 of pump 52,represented by shaft 178. Because of the structure of shaft 162 betweenthe pistons of motor 54 and pump 52, all pistons have a similar travel.Preferably, the cylinders have length only slightly greater than thepiston travel. In this way, when sensing switch 112 senses the end oftravel of piston 72 or when sensing switch 122 senses the end of travelof piston 74, the stroke of any particular piston moves through most ofthe length of the particular cylinder. In any case, when valve 164switches, chamber 152 and chamber 158 are at maximum volume, whilechamber 154 and chamber 156 are at a minimum volume. As shown in FIG.4B, when valve 164 changes position, chamber 156 is open to the highpressure, saturated third liquid to initiate the hydraulic power strokeof piston 150 and chamber 158 is open to exhaust. At the same time,chambers 152 and 154 are placed in fluid communication with one anotherto form a motor chamber and begin the expansion power stroke of piston148. When pistons 148 and 15 reach the extent of travel in the oppositedirection, switching again takes place and the motor continues to cycle.

Ideally, the pressure of the liquid/gas mixture leaving either of thesecond portions of the main chambers when they function to exhaust, andthe pressure in drain line 170 are the same. If the spent mixed-phasemixture has not been expanded sufficiently, the mixture expands furtherinto drain valve 170, as valve 164 switches and work is lost. If thespent mixed-phase mixture has been expanded too much, flow in drain line170 reverses to fill the second portion of the chamber temporarily whenvalve 164 shifts.

Coupling the shaft work output of drive shaft 162 of motor 54 to theshaft work of rod 84 of pump 52 results in pump-motor 50 energyrecovery. Pump-motor 50 thus captures both flow-work from all of first,second, and third liquids to some degree, primarily flow-work howeverfrom the high pressure liquids, and expansion work from the saturatedthird liquid and transfers the energy to desired flow-work bypressurizing and pumping the first liquid.

When energy from the various streams is insufficient to raise firstliquid pressure as desired, a standard pump may be added.

The pistons of pump 52 and motor 54 are coupled together. In addition,the switching valve 106 of pump 52 is connected with the switching valve164 of motor 54. They must both shift at the same time to avoidhydraulic lock-up of pump-motor 50. Timing of the switching may be basedon any of several criteria, for example, piston reaching the end of achamber, pressure within the chamber, etc. In any case, the variouspistons need not travel the full extent possible. Incomplete travelallows for adjustment of the ratios of initial and final volumes of workextraction from motor 54. Full travel, however, provides optimum use ofavailable expansion volumes, provided the motor has been properly sizedfor the fluid properties of the system in which pump-motor 50 isincorporated.

System Applications

A conventional absorption refrigeration and/or heating system is shownin FIG. 1 and designated by the numeral 10. System 10 was describedhereinbefore. A system 180 which replaces valve 20 of system 10 with anenergy recovery pump 52, is shown in FIG. 3. In this regard, it is notedthat hereinafter alternate embodiments and components thereof aredesignated by identical numerals as earlier used, except the numeralsare primed to distinguish among the embodiments. As indicated, pump 52'is installed in place of valve 20 to recover energy from the weaksolution depressurized thereby and is inserted in line 40 of FIG. 1. Inthat way, pump 36 of FIG. 1 need not supply all the energy needed toraise the pressure of the strong solution.

With respect to pump 52', it is noted that it is being usedindependently of motor 54 so that there is no drive shaft 162 or dummyshaft 180, and there is no connecting shaft 178 or other mechanism forconnecting with a valve of motor 54. In all other respect, pump 52' isthe same as pump 52, and the description given hereinbefore is accuratewith respect to pump 52'.

With respect to installation in system 180, line 102' directs highpressure, weak solution flow from desorber 12' to an input of valve106'. Low pressure, weak solution output of valve 106' is directed alongline 110' to absorber 114'. Low pressure, strong solution is directedfrom pump 136' along line 86' to one of check valves 90' and 92'. Highpressure, strong solution pumped by energy recovery pump 52' flows fromone of check valves 98' and 100' along line 96' to desorber 12.

The rest of system 180 is similar to system 110 in that vaporrefrigerant flows from desorber 12' along line 22' to condenser 24'.Liquid refrigerant then flows from condenser 24' along line 26' to bedepressurized at valve 30' before being directed by line 28' toevaporator 32'. Evaporated refrigerant flows from evaporator 32' alongline 34' to absorber 14'. From absorber 14', low pressure strongsolution is partially pressurized by pump 36' before being elevated todesired high pressure by energy recovery pump 52'.

Correct operation of a system like system 110 hinges on correct flowrates of refrigerant and working fluid in its strong and weak form. Anenergy recovery pump 52' is particularly advantageous because of itspositive displacement flow regulation characteristics. Pump 52' providessimple and direct means for fixing optimal mass flow ratios of fluids.System control problems are minimized.

Whereas leak rates are rather high in gear-type and van-type pumps andmotors, a piston device like pump 52' advantageously has low leak ratesto essentially no leakage. This further ensures conclusivelydeterminable flow ratios, whereas in other types of devices varyingdegrees of leakage must be accounted for.

An additional advantage with an energy recovery pump 52' is that apiston-type device has substantially lower mechanical friction lossesthan other devices and is therefore more efficient. Additionally, fluidfriction losses are also substantially lower, leading to yet higherefficiency.

Whereas energy recovery pump 52' replaces one valve and supplies atleast some of the pumping capacity, an energy recovery pump-motor, suchas 50, can be used to replace two valves and a pump. In this regard, asshown in FIG. 2, a system 182 incorporates a pump-motor 50 to replacepump 36, valve 20 and valve 30 of system 10.

Energy recovery pump-motor 50" is exactly the same as that describedwith respect to FIGS. 4A and 4B. Low pressure, strong solution fromabsorber 14" is directed through line 86" to pump 52". High pressure,strong solution leaves pump 52" along line 96" to desorber 12". Highpressure, weak solution leaves desorber 12" along line 102" and isdirected to pump 52". Expended low pressure, weak solution leaves pump52" along line 110" leading to absorber 14". Vapor refrigerant flowsfrom desorber 12" to condensor 24" via line 22". High pressure, liquidrefrigerant leaves condenser 24" via line 168" to flow to mixed-phasemotor 54". The spent low pressure, mixed-phase liquid/vapor from motor54" is directed via line 170" to evaporator 32". Evaporated refrigerantflows from evaporator 32" to absorber 14" via line 34".

Pump-motor 50 is particularly advantageous with respect to system 182 inthat pump 36 of system 10 may be completely eliminated since the energyrecovered in replacing valves 20 and 30 of system 10 is ordinarily morethan sufficient to pump strong solution to the desired high pressure. Itis noted, however, that it may be desirable to use a small pump toregulate flow and provide start up flow.

Pump-motor 50 is further advantageous with respect to system 182 in thatthe refrigerant leaving motor 54" for evaporator 32" has a greaterliquid to vapor ratio than occurs in system 10. As a result, heat, Q3,extracted from the environment to evaporator 32" is increased. In otherwords, in a refrigeration mode, greater cooling at less cost isachieved.

Another application of pump-motor 50 in accordance with the presentinvention relates to a double-effect absorption refrigeration and/orheating system. A conventional system of the prior art is shown in FIG.5. Strong solution leaving absorber 184 is directed via lines 186 and188 through pump 190. Strong solution entering primary desorber 192 athigh pressure forms an intermediate strength solution after highpressure refrigerant is evaporated off by heat addition, Q1.Intermediate strength solution thus formed is throttled through valve194 to secondary desorber 196 via lines 198 and 200. Heat is added tothe secondary desorber 196 from both Q1' and by condensation of highpressure refrigerant evaporated in primary desorber 192 and passedthrough secondary desorber 196 via line 202. Weak solution from thesecondary desorber then passes through valve 204 to the low pressureabsorber 184 via lines 206 and 208.

High pressure, high temperature, liquid refrigerant condensed insecondary desorber 196 is throttled through valve 210 to form aliquid/vapor mixture which enters condenser 212 via line 214. Thismixture combines with the vapor refrigerant evaporated in secondarydesorber 196 and directed to condenser 212 via line 216. The vaporrefrigerant and liquid/vapor mixture are condensed before flowing fromcondenser 212 through valve 218 to evaporator 220 via lines 222 and 224.The liquid portion of the mixture from condenser 212 is evaporated inevaporator 220 with heat, Q3, absorbed from the environment. Finally,the low pressure, refrigerant vapor flows from evaporator 220 via line226 to remix with weak solution in absorber 184. Heat, Q4, is given offand strong solution is formed to renew the cycle.

The double effect system of FIG. 5 also ordinarily includes heatexchangers. For the sake of clarity, they are not shown. Ordinarily,however, a first heat exchanger includes line 188 and 198, while asecond heat exchanger includes lines 222 and 226.

As shown in FIG. 6, two energy recovery pump-motors 50 may be used in adouble effect system to replace the valves and pump. The firstpump-motor 50 replaces valves 194 and 210, as well as providing some ofthe pumping capacity. The second pump-motor 50 replaces valves 204 and218 and provides the remainder of needed pumping capacity. Eachpump-motor 50 is exactly the same as that disclosed in FIGS. 4A and 4B.

Low pressure, strong solution is directed via line 86'" from absorber184' to the second of pump-motors 50, identified by the numeral 502. Thefirst liquid leaves pump-motor 502 at a higher pressure via line 96'"and is input into the first of pump-motors 50, identified by the numeral501. After being elevated to a still higher pressure, first liquidleaves pump-motor 501 via line 96"" and is directed to primary desorber192'. High pressure intermediate solution is directed from primarydesorber 192' to pump-motor 501 via line 102"". After yielding some ofits energy, intermediate solution flows from pump-motor 501 via line110"" to secondary desorber 196'. From secondary desorber 196', the nowweak solution having an intermediate pressure level is directed via line102'" to pump-motor 502. After yielding the rest of its hydraulicenergy, weak solution leaves pump-motor 502 at a low pressure level andflows via line 110'" to absorber 184'.

Vapor refrigerant is directed from parimary desorber 192' to secondarydesorber 196' via line 202'. The high pressure, now liquid refrigerant,continues to flow from secondary desorber 196' to pump-motor 501 vialine 168"". After giving up its work potential at pump-motor 501, thevapor/liquid mixture flows via line 170"" to condenser 212'. Fromcondenser 212', the liquid refrigerant at an intermediate pressure levelflows via line 168'" to pump-motor 502 to epend additional expansionenergy and then flow via line 170'" to evaporator 220'. From evaporator220', the now evaporated refrigerant is directed via line 226', toabsorber 184', to be remixed with weak solution to recharge the systemand continue the cycle.

The energy recovery pump-motor of the present invention is advantageouswithin a double effect absorption system for the same reasons that it isadvantageous in a single effect absorption system described with respectto FIG. 2. Additionally, use of a pair of pump-motors 50 in a doubleeffect system reduces energy loss as low grade heat at condenser 212' byextracting the energy as useful work at pump-motor 501. In other words,the fluid mixture entering the condenser has a greater percentage ofliquid than would otherwise be the case if pump-motor 501 were not inthe system. There is thus proportionately less vapor to be condensed.Therfore, less heat, Q2, is given off and sytem efficiency is increased.

Thus, a number of systems showing application for the energy recoverydevice of the present invention and the advantages of the device withineach particular system have been described in detail. It is understood,however, that many additional applications are likely and are alsounderstood to coprise the invention as equivalents.

Structural Relationships

When incorporating an energy recovery pump-motor 50 in a particularfluid system, a thermodynamic analysis of the system must be done inorder to size the various components with respect to temperature,pressure, volume, change of phase, etc., of fluid as it cycles throughthe system. For the purpose of the present disclosure, it is sufficientto present the relationships appropriate for sizing a pump-motor 50relative to system parameters which would become known after doing theindicated thermodynamic analysis.

The system parameter to which the size of the various elements of thepump-motor 50 will be related is specific volume, having units ofvolume/mass. A phase diagram of pressure versus specific volume is shownin FIG. 7 and has been drawn with reference to an absorptionrefrigeration system of the types described hereinbefore. With respectto a phase diagram, it is noted that the state of a substance can beconclusively determined by considering a horizontal line which starts atthe left vertical margin of the chart, passes through the characteristicdome, and continues toward the right out of the dome. States along theline to the left of the dome are subcooled liquid. A subcolled liquidrequires some quantity of heat to increase its temperature before it canbegin to form a vapor. The point where the line contacts the left sideof the dome is the point where vapor is just about to form. At thispoint, the liquid is saturated and on the addition of more heat at aconstant pressure, vapor will form. As the line proceeds through thedome, more and more vapor is generated until the right side of the domeis reached. At that point, all the substance is vapor. From that pointto the right, the substance becomes superheated vapor.

With reference to FIGS. 1 and 7, circle 1 indicates the fluid materialstate of the vapor in the desorber. Circle 2 indicates the state of thevapor refrigerant as it enters the condenser. Circle 3 indicates thestate of the liquid refrigerant as it leaves the condenser. Circle 4hindicates the liquid/vapor mixture after passing through a valve. circle5v shows the state of the mixture after being completely evaporated bythe evaporator. The broken line leading from circle 5v to circle 1depicts the various processes taking place between the evaporator andthe circle 1 state at the desorber as the cycle continues. It is notedthat circle 4h represents an ideal valve, while circle 4s represents anideal mixed-phase motor. Circle 4sa represents an actual mixed-phasemotor 54. That is, an actual motor 54 includes various inefficiencies.In any case, it is clear from the study of thermodynamics that while avalve is effective to control pressure in absorption refrigerationsystems, work is lost at the valve. A liquid passing through a valveloses flow-work or hydraulic pressure energy irreversibly to heat. Avapor or a liquid which is changing phase loses energy as itdepressurizes through an irreversible expansion. A pump-motor 50recovers both flow work energy and expansion energy. The recovery ofexpansion energy results in the movement to the left of the fluidrepresented by state circle 4sa relative to state circle 4h.

Two relationships are readily developed for relating specific volumes tothe various diameters of pump 52 and motor 54 of pump-motor 50. Withrespect to motor 54, it is observed that the mass of saturated liquidentering motor 54 is conserved and is the same as the mass ofmixed-phase liquid/vapor exhausting motor 54. On expressing the volumeof substance in terms of mass and specific volume and observing that theinitial and final masses are constant, the following relationshipgoverns: (see FIGS. 4A and 7): ##EQU1## It is noted that symmetry forboth sides of both pump 52 and motor 54 is preferred so that oppositesides of each device operate 108° out of phase with one another.

To develop a relationship relating parameters of pump 52 and motor 54,conservation of mass is again used. It is noted that the mass flow rateof strong solution must equal the mass flow rate of weak solution and ofrefrigerant. On expressing mass flow rate in terms of specific volume,piston face area and piston velocity, the following relationshipresults: ##EQU2## In the case where there is only an energy recoverypump 52 in the system, d₀ and d₁ equal zero and the first of the aboveequations is not relevant.

With respect to system 180 wherein only pump 52' is incorporated in anabsorption refrigeration system, again a relationship between systemparameters and varoius diameters of pump components can be developedusing the conservation of mass principle. By equating the mass flow rateof strong solution at pump 52' to the mass flow rate of weak solution atpump 52' plus the mass flow rate of refrigerant which can readily beobtained at the exhaust port of condenser 24', and rewriting the massflow rates in terms of relevant component diameters and system specificvolumes, the following rationship results (see FIGS. 4A and 7): ##EQU3##

Thus, the energy recovery pump-motor 50 of the present invention hasbeen described in detail and related to a number of system applications.Furthermore, advantages of the invention and its applications have beennoted and relationships provided for sizing the invention relative to aparticular system. It is understood, however, that the invention isconceptual and that numerous equivalents are possible. Consequently, itis further understood in conclusion that any changes made from thedisclosure as presented, especially in matters of design, shape, size,and arrangement of parts to the full extent extended by the generalmeaning of the terms in which the appended claims are expressed, arewithin the principle of the invention.

What is claimed is:
 1. Energy recovery apparatus, comprising:a pump witha driving chamber and a pumping chamber and first means forreciprocating to simultaneously increase the size of one of said drivingand pumping chambers and decrease the size of the other, said pumphaving means for filling said pumping chamber with a first liquid offirst pressure, said pump further having means for driving said firstreciprocating means in a pumping stroke with a second liquid at a secondpressure in said driving chamber, said pump including means forreleasing said first liquid from said pumping chamber during saidpumping stroke, said pump also including first means for returning saidfirst reciprocating means and filling said pumping chamber with more ofsaid first liquid in a filling stroke, said pump further including firstmeans for exhausting said second liquid from said driving chamber duringsaid filling stroke; a motor with a main chamber and a second means forreciprocating which divides said main chamber into first and secondportions, said motor including means for placing said first portion influid communication with a third liquid at a third pressure to move saidsecond reciprocating means through a hydraulic power stroke, said motorfurther having means for allowing expansion of said third liquid intoboth said first and second portions to change phase and form a vapor andliquid mixture to drive said second reciprocating means in an expansionpower stroke, said motor including second means for exhausting spentvapor and liquid at a pressure lower than said third pressure from saidsecond portion during said hydraulic power stroke; means for connectingsaid first and second reciprocating means for simultaneous movements;and means for switching from one of said pumping and filling strokes toanother and from one of said hydraulic and expansion power strokes toanother at the same time; whereby said pump and said motor recoverenergy from said second and third liquids to pump said first liquid. 2.Energy recovery apparatus, comprising:a pump with a first cylinder and afirst piston therein dividing said first cylinder into a driving chamberand a pumping chamber, said pump having means for filling said pumpingchamber with a first liquid of first pressure, said pump further havingmeans for driving said first piston in a pumping stroke with a secondliquid at a second pressure in said driving chamber, said pump includingmeans for releasing said first liquid from said pumping chamber duringsaid pumping stroke, said pump also including first means for returningsaid first piston in a filling stroke, said pump further including firstmeans for exhausting said second liquid from said driving chamber duringsaid filling stroke; a motor with a second cylinder and a second pistontherein dividing said second cylinder into first and second portions,said motor having means for placing said first portion in fluidcommunication with a third liquid at a third pressure to move saidsecond piston through a hydraulic power stroke, said motor furtherhaving means for allowing expansion of said third liquid into saidsecond portion to change phase and form a vapor and liquid mixture todrive said second piston in an expansion power stroke, said motorincluding second means for exhausting spent vapor and liquid at apressure lower than said third pressure from said second portion duringthe hydraulic power stroke, said motor further including second meansfor returning said second piston in said hydraulic power stroke; meansfor connecting said first and second pistons for simultaneous movements;and means for switching from one pump stroke to another and from onemotor stroke to another at the same time; whereby said pump and saidmotor recover energy from said second and third liquids to pump saidfirst liquid.
 3. Apparatus in accordance with claim 2 wherein saiddriving and pumping chambers are first driving and pumping chambers,said filling means is a first filling means, said driving means is afirst driving means, and said releasing means is a first releasingmeans, said first returning means of said pump including a thirdcylinder and a third piston therein to divide said third cylinder into asecond driving chamber and a second pumping chamber, said firstreturning means also having second means for filling said second pumpingchamber with the first fluid of first pressure, said first returningmeans further having second means for driving said third piston in apumping stroke to pump said first liquid with the second liquid at thesecond pressure in said second driving chamber, said first returningmeans including second means for releasing said first liquid from saidsecond pumping chamber during the pumping stroke of said second piston,said first returning means further including third means for exhaustingsaid second liquid from said second driving chamber during the fillingstroke of said third piston, said first switching means including meansfor controlling said first and third pistons so that when said firstpiston is in a pumping stroke, said third piston is in a filling strokeand vice versa.
 4. Apparatus in accordance with claim 3 wherein saidplacing means is a first placing means, said expansion allowing means isa first expansion allowing means, said second returning means of saidmotor including a fourth cylinder and a fourth piston therein to dividesaid fourth cylinder into third and fourth portions, said secondreturning means having second means for placing said third portion influid communication with the third liquid to move said fourth pistonthrough a hydraulic power stroke, said second returning means furtherhaving means for allowing expansion of the third liquid into said fourthportion to change phase and form a vapor and liquid mixture to drive thefourth piston in an expansion power stroke, said second returning meansalso including fourth means for exhausting spent vapor and liquid duringthe hydraulic power stroke, said second switching means also includingsecond means for controlling movement of said second and fourth pistonsso that when said second piston is in an expansion power stroke, saidfourth piston is in a hydraulic power stroke and vice versa. 5.Apparatus in accordance with claim 4 wherein said first controllingmeans includes a four-way, two position valve, said valve in a firstposition allowing a first portion of said second liquid into said firstdriving chamber and allowing a second portion of said second liquid toexhaust from said second driving chamber and vice versa when said valveis in said second position.
 6. Apparatus in accordance with claim 5wherein said second controlling means includes a eight-way, two positionvalve, said valve in a first position allowing the third liquid to flowinto the first portion of said second cylinder and spent third liquidand vapor fluid to flow from the second portion of said second cylinderand third liquid in said third portion of said fourth cylinder to expandinto said fourth portion of said fourth cylinder and vice versa whensaid valve is in said second position.
 7. Apparatus in accordance withclaim 6 wherein said switching means further includes means for movingsaid four-way valve and said eight-way valve between positionssimultaneously.
 8. Apparatus in accordance with claim 7 wherein saidswitching means still further includes means for sensing one of saidfirst, second, third, and fourth pistons near an end of travel in onedirection and second means for sensing one of said first, second, third,and fourth pistons near an end of travel in an opposite direction.
 9. Anenergy recovery apparatus, comprising:a pump with first and secondaligned cylinders with first and second pistons therein, respectively,said pistons being connected together with a rod, said first and secondpistons dividing said first and second cylinders into first and seconddriving and pumping chambers, respectively, said rod which connects saidpistons together passing through said driving chambers, each of saidpumping chambers including first and second check valves, said firstcheck valves allowing fluid to pass into said pumping chambers and saidsecond check valves allowing fluid to pass out of said pumping chambers,said pump further including a four-way, two-position valve, said valvehaving an input and an output, said valve in said first position placingsaid input in fluid communication with said first driving chamber andsaid output in fluid communication with said second driving chamber,said valve in said second position placing said input in fluidcommunication with said second driving chamber and said output in fluidcommunication with said first driving chamber, said pump also includingmeans for switching said four-way valve between said positions, saidswitching means including first and second means for sensing one of saidfirst and second pistons at opposite ends of travel of said pistons; amotor having third and fourth cylinders and third and fourth pistonsdividing each of said third and fourth cylinders into first and secondportions, said motor also having a second rod connecting said third andfourth pistons together, said second rod passing through said secondchambers, said motor further having an eight-way, four-position valve,said eight-way valve having a second input and a second output, saidfour-way valve in said first position placing said input in fluidcommunication with said first portion of said third cylinder and placingsaid output in fluid communication with said second portion of saidthird cylinder and placing said first and second portion of said fourthcylinder in fluid communication with one another, said eight-way valvein said second position placing said input in fluid communication withsaid first portion of said fourth cylinder and placing said output influid communication with said second portion of said fourth cylinder andplacing said first and second portions of said third cylinder in fluidcommunication with one another; a drive shaft for connecting one of saidfirst and second pistons with one of said third and fourth pistons, saiddrive shaft having a cross-sectional area; dummy shaft means forextending from the other of said first and second pistons than isattached to said drive shaft to a wall of said cylinder opposite saidother piston, said dummy shaft extending means having the samecross-sectional area as said drive shaft; and means for controlling saideight-way valve and said four-way valve to change positions at the sametime; wherein when said four-way valve and said eight-way valve are infirst positions, said first piston moves through a pumping stroke, saidsecond piston moves through a filling stroke said third piston movesthrough a hydraulic power stroke and said fourth piston moves through anexpansion power stroke, and vice versa for said first and second pistonsand said third and fourth pistons when said four-way valve and saideight-way valve are in second positions.
 10. A method for using anenergy recovery apparatus to transfer energy from first and secondpressurized liquids to a third liquid, said energy recovery apparatusincluding a pump with a driving chamber and a pumping chamber and firstmeans for reciprocating to simultaneously increase the size of one ofthe driving and pumping chambers and decrease the size of the other,said pump having means for filling the pumping chamber with the firstliquid of a first pressure, said pump further having means for drivingthe first reciprocating means in a pumping stroke with the second liquidat a second pressure in the driving chamber, said pump including meansfor releasing the first liquid from the pumping chamber during thepumping stroke, said pump also including first means for returning thefirst reciprocating means in a filling stroke, said pump furtherincluding first means for exhausting the second liquid from the drivingchamber during the filling stroke, said energy recovery apparatusfurther including a motor with a main chamber having first and secondportions and second means for reciprocating to simultaneously increasethe size of one of the first and second portions and decrease the other,the motor having means for placing said first portion in fluidcommunication with the third liquid at a third pressure to move saidsecond reciprocating means in a hydraulic power stroke, the motorfurther having means for allowing expansion of the third liquid into thesecond portion to change phase and form a vapor and liquid mixture todrive the second reciprocating means in an expansion power stroke, themotor including second means for exhausting spent liquid and vapor at apressure lower than the third pressure from the second portion duringthe hydraulic power stroke, the motor further including second means forreturning the second reciprocating means in the hydraulic power stroke,said energy recovery apparatus further having means for connecting thefirst and second reciprocating means for simultaneous movement and meansfor switching from one pump stroke to another and from one motor stroketo another at the same time, said method comprising the stepsof:directing second liquid into said driving chamber to force said firstreciprocating means in a pumping stroke, thereby pumping first liquidfrom said pumping chamber and placing said first portion of said mainchamber in fluid communication with a third liquid at a third pressureto drive said second reciprocating means in a hydraulic power strokewhile exhausting third liquid at a lower pressure from said secondportion; and filling said pumping chamber with first liquid at a firstpressure while exhausting second liquid from said driving chamber andexpanding said third liquid from said first portion into said secondportion to form a vapor and liquid mixture and drive said secondreciprocating means in an expansion power stroke.